Nov.
30, 2006 — As the 2006
Atlantic hurricane season comes to a close today, NOAA
scientists announced that seasonal activity was lower than expected
due to the rapid development of El Niño—a
periodic warming of the ocean waters in the central and eastern equatorial
Pacific, which influences pressure and wind patterns across the tropical
Atlantic. (Click NOAA satellite image for larger view of Tropical
Storm Ernesto taken on Aug. 31, 2006, at 10:45 a.m. EDT. Click
here for high resolution version. Please credit “NOAA.”)

The 2006 Atlantic hurricane season produced near-normal activity with
a total of nine named storms, including five hurricanes, two of which
became major hurricanes of Category 3 strength or higher. An average
Atlantic hurricane season has 11 named storms, with six becoming hurricanes
and two becoming major hurricanes. Unlike the past three seasons, the
stronger hurricanes stayed well out at sea, sparing the Americas and
the Caribbean islands from major hurricane damage this season.

“The
development of El Niño conditions by September helps explain
why this Atlantic hurricane season was less active
than predicted,” said Gerry Bell,
NOAA’s lead forecaster on the Atlantic hurricane seasonal outlook
team. “El Niño developed quickly and the atmosphere responded
rapidly, reducing hurricane activity during an otherwise active era
that began in 1995.” (Click NOAA image for larger view
of explanation as to why the 2006 Atlantic hurricane season turned out
less active than predicted. Click
here for high resolution version. Please credit “NOAA.”)

El Niño, combined with the large-scale weather patterns over
the southeastern U.S., produced sinking air in the middle and upper
atmosphere, along with higher than anticipated wind shear (the change
in winds through the atmosphere) over the Atlantic Ocean, Gulf of Mexico
and Caribbean Sea. These conditions minimized thunderstorm activity,
which inhibited tropical storm and hurricane formation.

Analysis by NOAA scientists has linked El Niño’s rapid
development and intensification to a series of large subsurface ocean
waves that affect ocean temperatures, which began in June. These waves
produced a progressive warming of the tropical Pacific Ocean during
the summer months. A particularly strong wave led to a significant warming
of the entire eastern half of the equatorial Pacific in early September.
This led NOAA in early September to report that an El Niño had
developed. These warmer waters produced enhanced rainfall near the international
date line, resulting in suppressed hurricane activity.

“Getting
a quick handle on El Niño events, which rapidly intensify, is
essential for predicting seasonal hurricane activity,” said Bell.
“The last time we had a rapidly developing El Niño was
during the 2002 hurricane season, which also led to near-normal activity.
NOAA continues to develop and improve climate models to better predict
the onset of El Niño, its impacts on weather patterns in the
United States and its effects on Atlantic hurricane activity.”

To detect and monitor the formation, duration and strength of El Niño,
NOAA established the ENSO
Observing System in 1994. Today’s operational system is based
on work done by the Pacific Marine Environmental Laboratory, which is
a branch of NOAA Research. The ENSO Observing system is an example of
NOAA research activities being translated into operational forecast
products. NOAA’s operational ENSO observing system includes the
TAO/TRITON array of moored buoys and the Argo drift buoys that observe
ocean patterns in conjunction with NOAA’s polar orbiting satellites.
The satellites, in combination with the TOGA TAO operational array,
are critical for allowing NOAA to monitor, assess and predict El Niño
events. The data from the ocean observing system provides substantial
benefit to both NOAA's research and operational forecasts of climate
patterns that can strongly affect weather across the nation.

In 2007
NOAA, an agency of the U.S. Commerce
Department, celebrates 200 years of science and service to the nation.
Starting with the establishment of the U.S. Coast and Geodetic Survey
in 1807 by Thomas Jefferson much of America's scientific heritage is
rooted in NOAA. The agency is dedicated to enhancing economic security
and national safety through the prediction and research of weather and
climate-related events and information service delivery for transportation,
and by providing environmental stewardship of the nation's coastal and
marine resources. Through the emerging Global Earth Observation System
of Systems (GEOSS), NOAA
is working with its federal partners, more than 60 countries and the
European Commission to develop a global monitoring network that is as
integrated as the planet it observes, predicts and protects.